Much effort has been directed at improving the light stability of polymers, such as polyamides. One method of improving the light stability of polymers is to incorporate one or more components into the polymer structure, wherein the one or more components comprise a light-stabilizing moiety. When present in the polymer chain of the resulting polymer, the light-stabilizing moiety provides enhanced light stability to the polymer. For example, nylon and nylon fibers formed by the polymerization of caprolactam in the presence of a hindered piperidine compound such as 4-amino-2,2,6,6-tetramethylpiperidine (TAD) exhibit improved light stability due to the light-stabilizing TAD moiety as taught in U.S. Pat. Nos. 5,851,238; 6,136,433; and 6,150,496, all of which are assigned to BASF Corporation, Mt. Olive, N.J., the entirety of all of which is incorporated herein by reference.
In the above-mentioned BASF patents, the concentration of TAD moieties along a light-stabilized polymer chain is less than 2 weight percent. In most cases, light-stabilizing properties are obtained when the TAD concentration is less than about 0.5 weight percent, based on the weight of the polymer-forming monomers.
In some countries around the world, for example China, the capacity for manufacturing light-stabilized polymers containing hindered amine compounds, such as TAD, is limited or does not exist at all. Because of the tight supply of light-stabilized polymer in the world market, only a limited amount of light-stabilized polymer can be sold to these countries.
Further, the manufacturing capacity for producing light-stabilized polymers in the form of films and/or fibers is limited. Typically, when a manufacturing facility is set up to produce a particular light-stabilized polymer film or fiber, the facility produces the particular light-stabilized polymer film or fiber in great quantity to optimize manufacturing efficiency, and to minimize downtime resulting from changes in product line. Any way to improve manufacturing capacity and/or flexibility would benefit the film and fiber industry.
What is needed in the art is a method of making light-stabilized polymers and light-stabilized article such that manufacturing capacity and/or flexibility is improved.